In relational databases the number of disk accesses depends on the amount of data transferred from disk to main memory for processing the transactions. N-ary vertical partitioning of the relation can often result in a decrease in the number of disk accesses, since not all attributes in a tuple are required by each transactions. In this paper, a 0-1 integer programming model for solving n-ary vertical partitioning problem minimizing the number of disk accesses is formulated and a branch-and-bound method is used to solve it. A preprocessing procedure reducing the number of variables is presented. The algorithm is illustrated with numerical examples and is shown to be computationally efficient. Numerical experiments reveal that the proposed method is more effective in reducing access costs than the existing algorithms.